Boria-alumina catalyst base

ABSTRACT

A catalyst support comprised of boria and alumina is prepared by the hydrolysis of a mixture of boron alkoxide and aluminum alkoxide. The boria-alumina composition prepared in accordance with the invention can be readily formed for use as a support for catalysts useful in a number of hydrocarbon conversion processes. For example, the boria-alumina may be used as a support for various combinations of zeolite, nickel oxide and molybdenum oxide to produce a catalyst particularly useful in the hydrocracking of petroleum feedstocks.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preparation of catalyst supports and theiruse in hydrocarbon conversion processes. More particularly, thisinvention relates to the preparation of boria-alumina catalyst supportmaterials and their use in the hydrocracking of petroleum feedstocks.

2. Description of the Prior Art

Catalyst compositions comprising a major proportion of a support orcarrier material such as alumina, silica, silica-alumina, magnesiumoxide, clay, etc. and a minor proportion of one or more metal or metaloxides have been used for a variety of hydrocarbon conversion processes.These catalysts are ordinarily prepared by impregnating the support orcarrier material with an aqueous solution of a soluble form of a metalcatalyst component. The impregnated support material is then dried andcalcined to produce a solid supported catalyst comprising a metalcatalyst component.

Boria-alumina based catalysts are known to be useful for hydrocarbonconversions. The boria-alumina support material heretofore employed as acatalyst base is known to have been prepared by the hydrolysis of analuminum alkoxide with an aqueous solution of boric acid or by theimpregnation of alumina with a boron compound as shown in U.S. Pat. Nos.2,713,037 and 3,018,244, respectively. It is found, however, that theboria-alumina based catalyst prepared in accordance with this inventionis markedly superior to those boria-alumina based catalysts prepared byconventional methods.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved catalyst basecomprising boria and alumina is prepared by hydrolyzing a mixture ofboron alkoxide and aluminum alkoxide. After recovery and calcination ofthe product, the resulting boria-alumina material may then beincorporated with various known catalyst components to produce acatalyst composition useful in a variety of hydrocarbon conversionprocesses, particularly with respect to the hydrocracking of petroleumfeedstocks.

The aluminum alkoxides used herein may include any alkoxide whichcontains from 1 to 20, preferably 2 to 4 carbon atoms in the alkoxidegroup and which is soluble in the liquid reaction medium. Specificexamples of suitable aluminum alkoxides include, among others, aluminumsec-butoxide, aluminum ethoxide, aluminum iso-propoxide, aluminumpropoxide, aluminum n-butoxide and aluminum iso-butoxide. Mixed aluminumalkoxides such as those produced by oxidizing the growth product fromthe reaction of aluminum triethyl and ethylene are also suitable.

The boron alkoxides used herein may include any alkoxide which containsfrom 1 to 20, preferably 1 to 4 carbon atoms in the alkoxide group andwhich is soluble in the liquid reaction medium. Specific examples ofsuitable boron alkoxides include, among others, trimethyl borate,triethyl borate, tripropyl borate, and tributyl borate.

The boron alkoxide and aluminum alkoxide are hydrolyzed together in thepresence of a suitable solvent and water at a temperature ranging fromambient to the boiling point of the reaction mixture, usually in therange of 20° to 100°C., for a sufficient period of time to complete thedesired reaction, usually for a period of 1 to 4 hours. The molar ratioof boron alkoxide to aluminum alkoxide charged to the reaction mixturewill be in the range of 0.030:1.00 to 1.47:1.00. Preferably, therelative amounts of reactants will be adjusted to give a concentrationof boria in the boria alumina mixture of at least 5.0 wt. % so that themolar ratio of boron alkoxide to aluminum alkoxide charged to thereaction mixture will preferably be in the range of 0.077:1.00 to0.628:1.00. The amount of water utilized in the reaction mixture ispreferably sufficient to substantially complete the co-hydrolysis of theboron and aluminum alkoxides. In general, however, a 5-10% molar excessof water is added to ensure substantially complete hydrolysis of thereaction mixture. The boria-alumina composition prepared in the abovemanner will generally contain 2 to 50 wt. %, preferably 5 to 30 wt. %,boria.

The reaction mixture is usually conducted in the presence of an organicliquid which is inert to the reactants and acts as a solvent for thesystem. Suitable solvents include, among others, the C₁ -C₄ alcohols,such as methanol, ethanol, isopropanol, normal butanol, isobutanol,sec-butanol, and t-butanol. The amount of solvent used may range from 0to 200, preferably 50 to 100 volume part per 100 volume part of combinedalkoxide.

After the reaction is complete, the precipitate which has formed isfiltered, dried, calcined and combined (either prior or subsequent tocalcination) with a minor amount of catalytic materials. Calcination ofthe boria-alumina product is conveniently effected by heating at 800° to1200°F. for a period of 1 to 4 hours. Addition of the metals orcompounds thereof to the boria-alumina support or carrier material iseffected by known techniques such as impregnation and vapor deposition.

The boria-alumina composition prepared in accordance with the inventionhas a relatively high surface area and is easily formed by conventionalextrusion or pelleting operations into a desired shape. Accordingly, theboria-alumina material may be advantageously used as a support orcarrier for catalytic materials which function as hydrocarbon conversioncatalysts. In general, these metals or compounds of such metals areknown to include groups IB, IIA, IIB, IIIB, IVA, VB, VIB, VIIB and VIIIand rare earth Lanthanide Series as given in "Webster's Seventh NewCollegiate Dictionary", (1963) published by G. & C. Merriam Company.

The boria-alumina composition of the invention may also beadvantageously used as a support or carrier for crystallinealuminosilicates or zeolites effective in promoting hydrocarbonreactions. These crystalline aluminosilicates (zeolites) comprise one ormore natural or synthetic zeolites. Representative examples ofparticularly preferred zeolites are zeolite X, zeolite Y, zeolite L,faujasite and mordenite. Synthetic zeolites have been generallydescribed in U.S. Pat. Nos. 2,882,244, 3,130,007 and 3,216,789, thedisclosures of which are incorporated herein by reference.

The silica-alumina mole ratio of useful aluminosilicates is greater than2.5 and preferably ranges from about 2.5 to 10. Most preferably, thisratio ranges between about 3 and 6. These materials are essentially thedehydrated forms of crystalline hydrous siliceous zeolites containingvarying quantities of alkali metal and aluminum with or without othermetals. The alkali metal atoms, silicon, aluminum and oxygen in thezeolites are arranged in the form of an aluminosilicate salt in adefinite and consistent crystalline structure. The structure contains alarge number of small cavities, interconnected by a number of stillsmaller holes or channels. These cavities and channels are uniform insize. The pore diameter size of the crystalline aluminosilicate canrange from 5 to 15A and preferably from 6 to 13A.

The aluminosilicate component may comprise a sieve of one specific porediameter size or, alternatively, mixtures of sieves of varying porediameter size. Thus, for example, mixtures of 5A and 13A sieves may beemployed as the aluminosilicate component. Synthetic zeolites such astype-Y faujasites are preferred and are prepared by well-known methodssuch as those described in U.S. Pat. No. 3,130,007.

The crystalline aluminosilicate can be in the hydrogen form, in thepolyvalent metal form, or in the mixed hydrogen-polyvalent metal form.The polyvalent metal or hydrogen form of the aluminosilicate componentcan be prepared by any of the well known methods described in theliterature. Representative of such methods is ion-exchange of the alkalimetal cations contained in the aluminosilicate with ammonium ions orother easily decomposable cations such as methyl-substituted quaternaryammonium ions. The exchanged aluminosilicate is then heated at elevatedtemperatures of about 570° to 1112°F. to drive off ammonia, therebyproducing the hydrogen form of the material. The crystallinealuminosilicate composition will preferably contain less than about 6.0wt. % of the alkali metal oxide based on the final aluminosilicatecomposition and, more preferably, less than 2.0 wt. %.

The resulting hydrogen aluminosilicates can be employed as such, or canbe subjected to a steam treatment at elevated temperatures, i.e., 800°to 1300°F., for example, to effect stabilization thereof, againsthydrothermal degradation. The steam treatment, in many cases, alsoappears to effect a desirable alteration in crystal structures resultingin improved selectivity.

Crystalline aluminosilicates which have been exchanged with polyvalentmetal cations are particularly useful herein. Suitably, the exchangedpolyvalent metals are transition metals and are preferably selected fromGroup VIII of the Periodic Table. Preferred metals include cobalt,nickel, molybdenum, tungsten, platinum, palladium, and the like. Themost preferred metal is nickel. The amount of nickel (or other metal)present in the aluminosilicate (as ion-exchanged metal) can range fromabout 0.1 to 20% by weight based on the final aluminosilicatecomposition.

The mixed hydrogen-polyvalent metal forms of the aluminosilicates arealso contemplated. In one embodiment the metal form of thealuminosilicate is ion-exchanged with ammonium cations and thenpartially back-exchanged with solutions of the desired metal salts untilthe desired degree of exchange is achieved. The remaining ammonium ionsare decomposed later to hydrogen ions during thermal activation.

The boria-alumina composition is particularly useful as a catalyst basefor use in hydrocracking of petroleum feedstocks. Accordingly, theboria-alumina composition of this invention may advantageously becombined with one or more hydrogenating components comprising thetransitional metals, preferably selected from Groups VIB and VIII of thePeriodic Table. Examples of suitable hydrogenating metals which may besupported upon the boria-alumina composition include, among others,nickel, tungsten, molybdenum, cobalt, platinum, palladium, including theoxides and sulfides thereof. Mixtures of any two or more of suchhydrogenating components may also be employed. The total amount ofhydrogenating component supported on the boria-alumina base may rangefrom 0 to 60, usually 10 to 25, wt. % based on the total catalystcomposition. For hydrocracking, the zeolites or crystallinealuminosilicates which may be combined with the boria-alumina base willgenerally be in the hydrogen or ammonium form and/or be exchanged withmetal ions such as nickel, cobalt, tin, palladium, platinum and rareearths such as cerium, lanthanum, neodymium, etc.

For use in hydrocracking, the boria-alumina catalyst base of theinvention will be contacted with a petroleum feedstock at a temperaturein the range of about 400° to 850°F., a pressure of 200 to 2000 psig., afeed rate of 0.1 to 10.0 V/V/Hr. and a hydrogen rate of 500 to 10,000s.c.f./bbl. of feed.

The boria-alumina composition of the invention may also be used as acarrier or support for metals or compounds thereof useful fordesulfurization, denitrogenation, reforming and other hydrocarbonconversion processes. For example, when impregnated with cobalt, nickel,tungsten and/or molybdenum, the boria-alumina composition of theinvention is useful for the desulfurization and denitrogenation of bothlight and heavy petroleum fractions. In addition, the boria-alumina basemay be combined with various noble metals such as platinum for use inreforming.

The feedstock suitable for conversion in accordance with the inventionincludes any of the well-known feeds conventionally employed inhydrocarbon conversion processes. Usually they will be petroleumderived, although other sources such as shale oil are not to beexcluded. Typical of such feeds are heavy and light virgin gas oils,heavy and light virgin naphthas, solvent extracted gas oils, coker gasoils, steam-cracked gas oils, middle distillates, steam-crackednaphthas, coker naphthas, catalytically-cracked naphthas, cycle oils,deasphalted residua, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples further illustrate the present invention. Unlessotherwise specified, all percentages and parts are by weight.

EXAMPLE 1

This example describes the preparation of a catalyst for hydrocrackingto middle distillate products using boria-alumina prepared in accordancewith the invention by cohydrolysis of boron and aluminum alkoxides.

A mixture of 67.4 grams trimethyl borate and 637.0 grams aluminumsec-butoxide was hydrolyzed at 180°F. with a solution containing 187grams water and 1000 ml. isopropyl alcohol. The hydrolysis was carriedout by adding the alcohol-water solution to the metal alkoxide mixturewith stirring over a 3 hour period. A boria-alumina precipitate wasformed which was separated from the alcohol by filtration and dried in adraft oven overnight at about 160°F. A product containing 15 wt. % B₂ O₃and 85 wt. % Al₂ O₃ on a calcined basis was obtained.

The oven dried boria-alumina was dry blended with nickel exchanged Yzeolite which was prepared by exchange with nickel nitrate solution soas to contain 2.98 wt. % nickel on a calcined basis. The proportions ofnickel zeolite and boria-alumina were 80 wt. % boria-alumina and 20 wt.% nickel zeolite on a calcined basis. The boria-alumina/zeolitecombination was mulled with water and then extruded with a pistonextruder. The wet extrudates were dried overnight in a draft oven atabout 160°F. and then calcined 2 hours at 1000°F. Molybdenum was thenadded to the calcined extrudates using ammonium molybdate in enoughwater to give incipient wetness. After oven drying at 250°F., additionalnickel was added using nickel nitrate in enough water to give incipientwetness. The concentration of reagents was such that the finishedcatalyst contained 3.0 wt. % nickel oxide and 15.0 wt. % molybdenumtrioxide. The catalyst was dried overnight at 250°F. and then calcined 3hours at 1000°F. It had a surface area of 311 m² /g and a pore volume of0.48 cc/g.

EXAMPLE 2

This example describes the preparation of a catalyst comprisingboria-alumina prepared by impregnating an alumina with boric acid, whichis outside of the scope of the present invention.

The alumina was prepared by hydrolyzing 695 grams of aluminumsec-butoxide at 180°F. with a solution of 167.5 grams of water in 1000ml. of isopropyl alcohol. The hydrolysis was carried out by adding thealcohol-water solution to the aluminum sec-butoxide with stirring over a3 hour period. The alumina precipitate was separated from the alcohol byfiltration and dried in a draft oven overnight at about 160°F. A warmsolution (60°C.) containing 37.3 gms. of boric acid in 275 ml. water wasthen added to 152.3 grams of the oven dried alumina and the mixtureworked to make a uniform paste. The paste was then oven dried overnightat 250°F. These proportions gave a product containing 15 wt. % B₂ O₃ and85% Al₂ O₃ on a calcined basis. The oven dried material was then dryblended with enough of the same nickel zeolite used in Example 1 to givea calcined extrudate containing 20 wt. % nickel zeolite and 80 wt. %boria-alumina.

Extrusion, metals addition, drying, and calcining were then carried outusing the same procedure and conditions as in Example 1. The finalcatalyst contained 3.0 wt. % nickel oxide and 15.0 wt. % molybdenumtrioxide. It has a surface area of 342 m² g. and a pore volume of 0.64cc/g.

EXAMPLE 3

This example describes the preparation of a catalyst using boria-aluminaprepared by hydrolyzing an aluminum alkoxide with an aqueous solution ofboric acid as described in Example 4 of U.S. Pat. No. 2,713,037.

The boria-alumina was prepared by hydrolyzing 637 grams of aluminumsec-butoxide at 180°F. with a solution of 38.8 grams of boric acid and150.0 grams of water in 1000 ml. of isopropyl alcohol. It was necessaryto keep this solution at 140°F. in order to prevent the boric acid fromprecipitating. The hydrolysis was carried out by adding the water-boricacid-alcohol solution to the aluminum sec-butoxide with stirring over a3 hour period. The boria-alumina precipitate was separated from thealcohol by filtration and dried overnight in a draft oven at about160°F. The product, containing 15 wt. % B₂ O₃ and 85% Al₂ O₃ on acalcined basis, was then incorporated into a catalyst containing thesame amounts of nickel zeolite, nickel oxide, and molybdenum oxide as inExamples 1 and 2. The final catalyst had a surface area of 324 m² /g.and a pore volume of 0.58 cc/g.

EXAMPLE 4

This example describes the preparation of a catalyst using boria-aluminaprepared in still another manner outside the scope of the presentinvention.

216 grams of alumina monohydrate was ball-milled 16 hours with 53.3grams of boric acid crystals. The ball-milled mixture was then heatedfor 4 hours at 302°F. to react the boric acid with the aluminamonohydrate. In the same manner as Example 1, the product containing 15wt. % B₂ O₃ and 85% Al₂ O₃ on a calcined basis was then incorporatedinto a catalyst containing the same amounts of nickel zeolite, nickeloxide and molybdenum oxide as in Example 1. The final catalyst had asurface area of 287 m² /g. and a pore volume of 0.44 cc/g.

EXAMPLE 5

This example describes the preparation of a catalyst using boria-aluminaprepared as in Example 1 except that the proportions of reagents is suchthat the boria-alumina product contains 7.5 wt. % boria and 92.5 wt. %Al₂ O₃.

In this example, a mixture of 33.7 grams methyl borate and 669 grams ofaluminum sec-butoxide was hydrolyzed under the conditions of Example 1with a solution of 181 grams of water in 1000 ml. of isopropyl alcohol.After filtering and drying the boria-alumina was incorporated in themanner of Example 1 into a catalyst containing the same amounts ofnickel zeolite, nickel oxide and molybdenum oxide as in Example 1. Thefinal catalyst had a surface area of 367 m² /g. and a pore volume of0.47 cc/g.

EXAMPLE 6

The catalysts prepared as in Examples 1 to 5 were tested ashydrocracking catalysts to produce middle distillate. The feed used wasa Kuwait Vacuum Gas Oil with the properties shown in Table I. Processconditions were 2000 psig. pressure, 1.0 volumes of feed per hour pervolume of catalyst, and 10,000 SCF/B (standard cubic feet per barrel) ofhydrogen. Temperature was adjusted so as to give 50 volume percentconversion to products boiling below 570°F. Selectivity to 300°F.-570°F.product was measured by distillation. Prior to introducing liquid feedto the reactor, the catalysts were sulfided using 10% hydrogen sulfidein hydrogen. The results were summarized in Table II.

                  TABLE I                                                         ______________________________________                                        FEED ANALYSES                                                                                  Kuwait VGO                                                   ______________________________________                                        Sulfur, Wt. %      3.03                                                       Gravity, °API                                                                             20.2                                                       Pour Point, °F.                                                                           105                                                        Nitrogen, ppm      879.6                                                      Distillation       D-1160                                                     Initial B.P., °F.                                                                         798                                                         5%                825                                                        10%                837                                                        20%                850                                                        30%                862                                                        40%                874                                                        50%                886                                                        60%                898                                                        70%                913                                                        80%                937                                                        90%                963                                                        95%                986                                                        Final B.P., °F.                                                                           1028                                                       Rec., %            99.0                                                       Res., %            1.0                                                        ______________________________________                                    

                  TABLE II                                                        ______________________________________                                                                 Selectivity to                                                                300-570°F. Product                            Catalyst °F. Required for                                                                       at 50% Conversion,                                   Example  50% Conversion  Vol. %                                               ______________________________________                                        1        726             70                                                   2        722             47                                                   3        735             44                                                   4        734             51                                                   5        733             58                                                   ______________________________________                                    

It can be seen from the results shown above in Table II that of the fourcatalysts containing 15% B₂ O₃ in the base, the catalyst of Example 1 issubstantially more selective for producing middle distillates. Thecatalyst of Example 5, containing only 7.5% B₂ O₃ in the base butprepared in accordance with the invention is also more selective thanthe prior art catalysts of Examples 2, 3 and 4.

What is claimed is:
 1. A catalyst composition comprising:a. a metal orcompound of a metal selected from the group consisting of rare earth,Group IB, IIA, IIB, IIIB, IVA, IVB, VB, VIB, VIIB and VIII of thePeriodic Table and combinations thereof, and b. a boria-aluminacomposition prepared by hydrolysis of a mixture of aluminum alkoxide andboron alkoxide in the presence of water.
 2. The catalyst compositionaccording to claim 1 wherein said metal is selected from the groupconsisting of Group VIB, Group VIII and combinations thereof.
 3. Thecatalyst composition according to claim 2 wherein there is additionallypresent a crystalline aluminosilicate zeolite.
 4. The catalystcomposition according to claim 3 wherein said metal is selected from thegroup consisting of cobalt, nickel, molybdenum, tungsten, platinum,palladium and combinations thereof.
 5. The catalyst compositionaccording to claim 4 wherein said boria-alumina composition contains 5to 30 wt. % boria.
 6. The hydrocracking catalyst composition accordingto claim 5 wherein said crystalline aluminosilicate comprises apolyvalent metal selected from rare earth, Group VIII and combinationsthereof.
 7. A catalyst composition comprising:a. a metal or compound ofa metal selected from the group consisting of nickel, cobalt,molybdenum, tungsten and combinations thereof; b. a crystallinealuminosilicate zeolite prepared by exchange of the sodium form thereofwith a cation selected from the group consisting of hydrogen, nickel,cobalt, iron, rare earths and combinations thereof; and c. aboria-alumina composition prepared by hydrolysis of a mixture of boronalkoxide and aluminum alkoxide in the presence of water at a temperaturein the range of 20° to 100°C.